Add env variable flexibility to raem account setup

I've found that AMAZON_ACCESS_KEY_ID/AWS_ACCESS_KEY and AMAZON_SECRET_ACCESS_KEY/AWS_SECRET_KEY are used interchangeably throughout AWS docs and comparable tools.

Since these seem to be environment variables used throughout these toolchains, I thought it might be useful to add some flexibility to raem while creating a new account.  This is a change I've used locally for a while, but I always forget to push it upstream.